Type 1 diabetes mellitus (T1DM) is a chronic and potentially life-threatening condition affecting the production of insulin, with rapidly increasing incidence worldwide. The disease impacts on nearly all domains of life, including the physical, social, neurological and psychological. Adequate management of the disease requires careful monitoring and self-care to maintain glycaemic control. Executive function (EF) refers to a cluster of top-down cognitive processes engaged in the planning and completion of goal-directed behaviour allowing an individual to plan their actions, contemplate novel challenges, resist temptation and focus attention while avoiding distracting stimuli. Young adulthood represents an important developmental stage during which robust EF is essential. Previously limited research has explored the impact of T1DM on EF specifically within a young adult population. The current study recruited a sample of young adults between the ages of 16 and 24 withT1DM (n=14) and an age and gender matched control group (n=14) of non-diabetic individuals. Groups were assessed on measures of EF while maintaining blood glucose levels within a euglycaemic range. The central aims of the study were to compare and contrast the diabetic and control group EF performance, and to explore the relationship between diabetic related variables and measures of EF. It was found that the diabetic group committed significantly more errors than the control group on a test of set-shifting ability. It was also found that the relationship between performance-based tests of EF and a rating scale measure of EF was unique to each group. HbA1c, a measure of longer term glycaemic control, was found to be significantly related to a rating scale measure of EF but not performance-based measures. It was also found that mean blood glucose level during assessment was significantly related to performance on measures of working memory. Despite a limited sample size, the findings suggest that in a young adult population there is some evidence that T1DM is related to impairments in certain areas of EF — including set-shifting, inhibition and the higher-level construct of problem-solving ability. Future research could extend these findings by specifically exploring the relationship between trail-making tasks and rating scales of EF, examining the role of hot EF in diabetes self-care, and determining the sensitivity of specific EF to subtle changes in blood glucose within a euglycaemic range.